Progress 09/01/03 to 08/31/05
Outputs
During the project period a number of systematic investigations were conducted to study and develop microwave (MW) and radio frequency (RF, dielectric) as alternatives to: 1) conventional use of kiln heat treatment (HT) and 2) chemical fumigation with methyl bromide (MB) for the phytosanitation treatment of solid wood packing materials (SWPM). Significant numbers of experimental trials were performed applying both RF dielectric and 2450 MHz (2.45 GHz) MW irradiation to investigate treating efficacy. Experimentation included SWPM nested with varying insect pests, pinewood nematode (PWN) and thus far limited data on phytopathogenic fungi. From the results it appears a treating schedule of 62 degrees centigrade (C) with microwaves is acceptable to sterilize SWPM against insect pests and the PWN. Cerambycids compared to other study insects did tend to require higher temperature to achieve the same lethal affect. Overall, the research shows much shorter durations are
possible with dielectric irradiation and in particular MW for a proven level of exposure mortality. Trials with infested wood at low moisture content (near or below fiber saturation) with experiments designed to kill Asian longhorned beetle and cotton wood borer (CWB) larvae required only 30 seconds exposure to 2.45 GHz microwaves. Even treating extremely high moisture wood indicated cerambycid larvae could be effectively killed (100% observed mortality) within 5 minutes of 2.45 GHz microwave irradiation applying 1100 Watt (W) or 900W power. This duration is far more time efficient for inducing a known lethal effect compared with conventional HT (minimum 30 minutes at 56 degrees C) or MB fumigation, requiring from 30 minutes to 48 hours for effective penetration. Moisture content was identified as a critical parameter for microwave scale-up to commercial-size loads of SWPM. Additional trials to study microwave parameters showed energy density (total microwave power/wood volume) is an
acceptable parameter to predict lethal 2.45GHz microwave doses when moisture content is a constant. Experiments with an industrial MW oven with continuous conveying showed that core wood temperatures as low as 46 and 53 degrees C can be effective on CWB and PWN (100% mortality), respectively. Dielectric irradiation experiments were conducted exclusively with a batch (40 KW, 18 MHz) RF oven. The RF experiments were designed to target 60 or 65 degree C to induce a consistent lethal efficacy shown effective with microwave irradiation. Time of exposure was varied to obtain this set of fixed temperatures or set fixed times with measured temperatures. Regardless, RF irradiation on wood infested with cerambycids (larvae, pupae, and adult) was determined to have a lower treating efficacy (less than 100% observed morality). However, the efficacy of RF irradiation against plant pathogenic fungi does appear promising. More experimental work to investigate treatment efficacy of RF irradiation is
warranted. Additional research activities are being planned to examine 915 MHz microwave with higher energy penetration and characteristic differential heating of insects vs. the infested wood material.
Impacts
Insects and pinewood nematodes infesting wood materials are killed much faster with microwave treatment than with currently approved phytosanitary methods, including methyl bromide fumigation and conventional kiln ovens. Also, experiments in industrial microwave ovens with commercial-size loads showed that treatment efficacy could be improved even further with movement of the samples during exposure, suggesting that the most cost effective treatment schedule will involve a conveyor system. At this point, sufficient data have been collected on the efficacy of microwave energy for phytosanitary treatment to begin a dialogue with the International Forest Quarantine Research Group (IFQRG) about approval of this method. The IFQRG is responsible for making recommendations to the Internatinal Plant Protection Committee for approval of new phytosanitary methods. Adoption of microwave energy as an approved method will benefit the wood pallet manufacturing industry in the U.S.
and help diminish introductions of exotic wood-boring insects in wooden shipping materials. Adoption of microwave energy as a phytosanitary method will reduce the need for methyl bromide and likely prove to be more cost effective than currently available methods.
Publications
- Fleming, M.R., Janowiak, J.J., Halbrend, J.H., Bauer, L.S., Miller, D.L., Morewood, D. and Hoover, K. 2005. Feasibility of eradicating pinewood nematodes and cerambycid beetle larvae infesting lumber with commercial 2.45 GHz microwave equipment. In: T.F. Shupe and W.R. Smith (eds.) Pallet phytosanitation information for international trade. ISBN: 0-9763632-0-8. http:www.agctr.lsu.edu/palletsanitation/index.asp. LSU Ag Center. Baton Rouge, LA. In cooperation with USDA Forest Service, Wood Education Research Center and Limestone Bluffs RC&D.
- Fleming, M.R., Bhardwaj, M.C., Janowiak, J.J., Shields, J.E., Roy, R., Argawal, D.K., Bauer, L.S., Miller D.L. and Hoover, K. 2005. Noncontact ultrasound detection of exotic pests in wooden packing materials. Forest Products J. 55(6):33-36.
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Progress 01/01/04 to 12/31/04
Outputs
For this reporting period a number of experiments have been completed on microwave irradiation to treat solid wood packing material (SWPM) as an alternative to conventional heat sterilization, fumigation via methyl bromide (MB) or treating with chemical preservatives. These testing activities have included research applying laboratory and industrial scale microwave (MW) technology with the cooperative assistance from a MW equipment manufacturer. The efforts included both batch and continuous 2.45 MHz commercial equipment designs. Treating trials were conducted on red pine (Pinus resinosa) boards and cant material infested with the pinewood nematode (PWN) and cerambycid larvae. Mortality data was collected after irradiation treatments of 5 kW, 6 kW and 7 kW microwave power with time duration sufficient to target an internal temperature of 62 degree centigrade (C) for the wood samples with measurements taken in proximity of the PWN or larvae pest. For the experiments
freshly processed materials were sorted into four moisture content (MC) categories: very high (>150% MC), high (>110% MC), medium (>65% MC) and low (less than 60% MC). Regardless of moisture category, above 63 degree centigrade temperature the results indicated a 100% mortality on the cerambycid and PWN pests for the batch MW trials. The continuous microwave experiments showed 100% mortality was possible with lethal temperatures as low as 46 degree centigrade and 53 degree centigrade for larvae and PWN, respectively. Additional experiments are pending to further examine the lethal affect of 2.45 MHz microwave treatment working with other invasive wood pests. The investigative study is progressing to perform similar experiments with dielectric (i.e. radio-frequency) irradiation treatment. Other work scheduled shall examine the operation costs of conventional heat sterilization and MB fumigation for comparison to possible microwave and dielectric treating options.
Impacts
Results suggest commercial 2.45 MHz microwave can be considered technically feasible as an alternative approach for the phytosanitary treatment of solid wood packing materials.
Publications
- Fleming, M.R., Hoover, K. , Janowiak, J.J., Fang, Y., Wang, X., Liu, W., Yang, Y., Hang, X., Agrawal, D., Mastro, V.C., Shields, J.E. and Roy, R. 2003. Microwave irradiation of wood packing material to destroy the Asian longhorned beetle. Forest Prod. J. 53(1):46-52.
- Fleming, M.R., Janowiak, J.J., Kearns, J., Shield, J.E., Roy, R., Agrawal, D.K., Bauer, L.S., Miller, D.L. and Hoover, K. 2004. Parameters for scale-up of lethal microwave treatment to eradicate cerambycid larvae infesting solid wood packing materials. Forest Prod. J. 54(7/8):80-84.
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Progress 01/01/03 to 12/31/03
Outputs
During this initial startup period the researchers have focused on preparatory objectives including insect/fungi/nematode supply, equipment and facility modifications, and experimental design. A successful technique to mass culture the pinewood nematode (Bursaphelenchus xylophilus) has been developed for use to infect wood samples with subsequent experimentation to examine the time power matrix of microwave and dielectric irradiation as an alternative approach to treat solid wood packing material (SWPM). In addition our initial work has attempted to identify optimum procedures for recovery of the pinewood nematode (PWM) from infected samples for determinations of treatment efficacy. Actual laboratory test trials with the PWN are still pending with further work to standardize the experimental procedures. Researchers at Penn State University (University Park Campus) are working closely with the Fruit Research Center (Biglerville, PA) to assure a reliable and consistent
measurement scheme to define PWN mortality after treatment exposure. A review of scientific literature was completed to identify fungi that might be used, as well as determination of inoculation procedures, for investigation into the lethal affect of microwave and radio-frequency (i.e. dielectric) energy on thermophillic fungi with resistant to conventional heat-sterilization such as the current SWPM treatment approved by the International Plant Protection Commission. A study plan is being devised with coordinated efforts between PSU and the USDA Forest Products Laboratory (Madison, WI). This research effort shall include activities to characterize colonization rates on freshly harvested logs (Pinus spp) inoculated with species of sapstainers identified in the literature to be highly heat tolerant (e.g. Ophiostoma minus, O. pilferum and Ceratocystis coerulescens). Other preparations have involved the identification and supply of powder-post beetles, bark beetles and other infectious
wood-boring insects to be used in later stages of the project to study the effectiveness of microwave and dielectric treating schedules.
Impacts
These activities serve an important initial step before actual work in the laboratory to establish the relative effectiveness of microwave and dielectric treatments as alternative approaches to the use chemical fumigation or conventional heat sterilization for the phytosanitary control and spread of invasive pests associated with solid-wood packing materials.
Publications
- No publications reported this period
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